Order the wrong size pizza from Debonairs and you could pay up to 43% extra – here’s how to get the most pizza for the least money

• A simple bit of math about pizza sizes inspired us to run the numbers on Debonairs Pizza.
• We broke down the prices of each size of each flavour of Debonairs pizza by the square centimetre.
• The result: Debonairs charges more, per square centimetre, for its medium pizzas than for its small versions – in one case sightly over 43% more. 

Depending on which flavour of pizza you order, you could pay as much as 43% extra for every square centimetre of your pizza from Debonairs.

And if you love the 23 centimetre medium-sized pizzas from Debonairs, you are paying at least 14% more per square centimetre than you would if you stuck to the 19 centimetre small size on its menu.

Buy any large (30 centimetre) pizza instead, and you'll be paying somewhere in between.

Or, to put it more simply: at Debonairs a large pizza has a medium price, a small pizza has a small price – and a medium pizza has a supersized price.

See also: Food is up to 32% more expensive on Uber Eats and Mr D than in-store – and that’s before delivery fees

On 7 January academic-paper software company Fermat’s Library tweeted a simple but attention-grabbing piece of math about pizza sizes, highlighting the difference between the diameter of a pizza – the measurement the pizza industry uses – and the area of pizza that translates into.

That inspired Business Insider to crunch the numbers on South African pizza.

The area of a circle is the square of the radius times Pi, or A= πr². This is the square centimetre breakdown of each of Debonairs' pizza sizes:

• 19cm small = 283.53cm²
• 23cm medium = 415.48cm²
• 30cm large = 706.86cm²

By area, a small Debonairs pizza is about 40% the size of a large, while a medium comes in at a little under 60% the size of the large.

But that is not reflected in the prices of the different sizes.

An analysis of Debonairs' pizza menu shows that, per square centimetre, medium pizzas are more expensive than large pizzas – and much more expensive than small pizzas.

The largest premium is on the simplest pizza, the Margherita. Per square centimetre Debonairs charges 43.03% more a medium Margherita than for a small version.

At the other end of the spectrum, the Debonairs Something Meaty carries only a 13.85% premium per square centimetre if you buy it in medium instead of small.

Here is how a selection of Debonairs pizzas stack up in price on a per-square-centimetre basis:

The short version: if you want to get the most bang for your pizza buck from Debonairs, stick to multiple small pizzas – or at least avoid the medium.

Asked about the difference in price between sizes, Debonairs said only that is "pricing strategy takes a number of factors into consideration including industry learnings" – and that it was not in a position to share details of its pricing strategy.